tests: Add fuzzing harness for CCoinsViewCache

2 files changed, 306 insertions, 0 deletions

diff --git a/src/test/fuzz/coins_view.cpp b/src/test/fuzz/coins_view.cpp
new file mode 100644
index 0000000000..52dd62a145
--- /dev/null
+++ b/src/test/fuzz/coins_view.cpp
@@ -0,0 +1,294 @@
+// Copyright (c) 2020 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#include <amount.h>
+#include <chainparams.h>
+#include <chainparamsbase.h>
+#include <coins.h>
+#include <consensus/tx_verify.h>
+#include <consensus/validation.h>
+#include <key.h>
+#include <node/coinstats.h>
+#include <policy/policy.h>
+#include <primitives/transaction.h>
+#include <pubkey.h>
+#include <test/fuzz/FuzzedDataProvider.h>
+#include <test/fuzz/fuzz.h>
+#include <test/fuzz/util.h>
+#include <validation.h>
+
+#include <cstdint>
+#include <limits>
+#include <optional>
+#include <string>
+#include <vector>
+
+namespace {
+const Coin EMPTY_COIN{};
+
+bool operator==(const Coin& a, const Coin& b)
+{
+    if (a.IsSpent() && b.IsSpent()) return true;
+    return a.fCoinBase == b.fCoinBase && a.nHeight == b.nHeight && a.out == b.out;
+}
+} // namespace
+
+void initialize()
+{
+    static const ECCVerifyHandle ecc_verify_handle;
+    ECC_Start();
+    SelectParams(CBaseChainParams::REGTEST);
+}
+
+void test_one_input(const std::vector<uint8_t>& buffer)
+{
+    FuzzedDataProvider fuzzed_data_provider{buffer.data(), buffer.size()};
+    CCoinsView backend_coins_view;
+    CCoinsViewCache coins_view_cache{&backend_coins_view};
+    COutPoint random_out_point;
+    Coin random_coin;
+    CMutableTransaction random_mutable_transaction;
+    while (fuzzed_data_provider.ConsumeBool()) {
+        switch (fuzzed_data_provider.ConsumeIntegralInRange<int>(0, 9)) {
+        case 0: {
+            if (random_coin.IsSpent()) {
+                break;
+            }
+            Coin coin = random_coin;
+            bool expected_code_path = false;
+            const bool possible_overwrite = fuzzed_data_provider.ConsumeBool();
+            try {
+                coins_view_cache.AddCoin(random_out_point, std::move(coin), possible_overwrite);
+                expected_code_path = true;
+            } catch (const std::logic_error& e) {
+                if (e.what() == std::string{"Attempted to overwrite an unspent coin (when possible_overwrite is false)"}) {
+                    assert(!possible_overwrite);
+                    expected_code_path = true;
+                }
+            }
+            assert(expected_code_path);
+            break;
+        }
+        case 1: {
+            (void)coins_view_cache.Flush();
+            break;
+        }
+        case 2: {
+            coins_view_cache.SetBestBlock(ConsumeUInt256(fuzzed_data_provider));
+            break;
+        }
+        case 3: {
+            Coin move_to;
+            (void)coins_view_cache.SpendCoin(random_out_point, fuzzed_data_provider.ConsumeBool() ? &move_to : nullptr);
+            break;
+        }
+        case 4: {
+            coins_view_cache.Uncache(random_out_point);
+            break;
+        }
+        case 5: {
+            if (fuzzed_data_provider.ConsumeBool()) {
+                backend_coins_view = CCoinsView{};
+            }
+            coins_view_cache.SetBackend(backend_coins_view);
+            break;
+        }
+        case 6: {
+            const std::optional<COutPoint> opt_out_point = ConsumeDeserializable<COutPoint>(fuzzed_data_provider);
+            if (!opt_out_point) {
+                break;
+            }
+            random_out_point = *opt_out_point;
+            break;
+        }
+        case 7: {
+            const std::optional<Coin> opt_coin = ConsumeDeserializable<Coin>(fuzzed_data_provider);
+            if (!opt_coin) {
+                break;
+            }
+            random_coin = *opt_coin;
+            break;
+        }
+        case 8: {
+            const std::optional<CMutableTransaction> opt_mutable_transaction = ConsumeDeserializable<CMutableTransaction>(fuzzed_data_provider);
+            if (!opt_mutable_transaction) {
+                break;
+            }
+            random_mutable_transaction = *opt_mutable_transaction;
+            break;
+        }
+        case 9: {
+            CCoinsMap coins_map;
+            while (fuzzed_data_provider.ConsumeBool()) {
+                CCoinsCacheEntry coins_cache_entry;
+                coins_cache_entry.flags = fuzzed_data_provider.ConsumeIntegral<unsigned char>();
+                if (fuzzed_data_provider.ConsumeBool()) {
+                    coins_cache_entry.coin = random_coin;
+                } else {
+                    const std::optional<Coin> opt_coin = ConsumeDeserializable<Coin>(fuzzed_data_provider);
+                    if (!opt_coin) {
+                        break;
+                    }
+                    coins_cache_entry.coin = *opt_coin;
+                }
+                coins_map.emplace(random_out_point, std::move(coins_cache_entry));
+            }
+            bool expected_code_path = false;
+            try {
+                coins_view_cache.BatchWrite(coins_map, fuzzed_data_provider.ConsumeBool() ? ConsumeUInt256(fuzzed_data_provider) : coins_view_cache.GetBestBlock());
+                expected_code_path = true;
+            } catch (const std::logic_error& e) {
+                if (e.what() == std::string{"FRESH flag misapplied to coin that exists in parent cache"}) {
+                    expected_code_path = true;
+                }
+            }
+            assert(expected_code_path);
+            break;
+        }
+        }
+    }
+
+    {
+        const Coin& coin_using_access_coin = coins_view_cache.AccessCoin(random_out_point);
+        const bool exists_using_access_coin = !(coin_using_access_coin == EMPTY_COIN);
+        const bool exists_using_have_coin = coins_view_cache.HaveCoin(random_out_point);
+        const bool exists_using_have_coin_in_cache = coins_view_cache.HaveCoinInCache(random_out_point);
+        Coin coin_using_get_coin;
+        const bool exists_using_get_coin = coins_view_cache.GetCoin(random_out_point, coin_using_get_coin);
+        if (exists_using_get_coin) {
+            assert(coin_using_get_coin == coin_using_access_coin);
+        }
+        assert((exists_using_access_coin && exists_using_have_coin_in_cache && exists_using_have_coin && exists_using_get_coin) ||
+               (!exists_using_access_coin && !exists_using_have_coin_in_cache && !exists_using_have_coin && !exists_using_get_coin));
+        const bool exists_using_have_coin_in_backend = backend_coins_view.HaveCoin(random_out_point);
+        if (exists_using_have_coin_in_backend) {
+            assert(exists_using_have_coin);
+        }
+        Coin coin_using_backend_get_coin;
+        if (backend_coins_view.GetCoin(random_out_point, coin_using_backend_get_coin)) {
+            assert(exists_using_have_coin_in_backend);
+            assert(coin_using_get_coin == coin_using_backend_get_coin);
+        } else {
+            assert(!exists_using_have_coin_in_backend);
+        }
+    }
+
+    {
+        bool expected_code_path = false;
+        try {
+            (void)coins_view_cache.Cursor();
+        } catch (const std::logic_error&) {
+            expected_code_path = true;
+        }
+        assert(expected_code_path);
+        (void)coins_view_cache.DynamicMemoryUsage();
+        (void)coins_view_cache.EstimateSize();
+        (void)coins_view_cache.GetBestBlock();
+        (void)coins_view_cache.GetCacheSize();
+        (void)coins_view_cache.GetHeadBlocks();
+        (void)coins_view_cache.HaveInputs(CTransaction{random_mutable_transaction});
+    }
+
+    {
+        const CCoinsViewCursor* coins_view_cursor = backend_coins_view.Cursor();
+        assert(coins_view_cursor == nullptr);
+        (void)backend_coins_view.EstimateSize();
+        (void)backend_coins_view.GetBestBlock();
+        (void)backend_coins_view.GetHeadBlocks();
+    }
+
+    if (fuzzed_data_provider.ConsumeBool()) {
+        switch (fuzzed_data_provider.ConsumeIntegralInRange<int>(0, 6)) {
+        case 0: {
+            const CTransaction transaction{random_mutable_transaction};
+            bool is_spent = false;
+            for (const CTxOut& tx_out : transaction.vout) {
+                if (Coin{tx_out, 0, transaction.IsCoinBase()}.IsSpent()) {
+                    is_spent = true;
+                }
+            }
+            if (is_spent) {
+                // Avoid:
+                // coins.cpp:69: void CCoinsViewCache::AddCoin(const COutPoint &, Coin &&, bool): Assertion `!coin.IsSpent()' failed.
+                break;
+            }
+            bool expected_code_path = false;
+            const int height = fuzzed_data_provider.ConsumeIntegral<int>();
+            const bool possible_overwrite = fuzzed_data_provider.ConsumeBool();
+            try {
+                AddCoins(coins_view_cache, transaction, height, possible_overwrite);
+                expected_code_path = true;
+            } catch (const std::logic_error& e) {
+                if (e.what() == std::string{"Attempted to overwrite an unspent coin (when possible_overwrite is false)"}) {
+                    assert(!possible_overwrite);
+                    expected_code_path = true;
+                }
+            }
+            assert(expected_code_path);
+            break;
+        }
+        case 1: {
+            (void)AreInputsStandard(CTransaction{random_mutable_transaction}, coins_view_cache);
+            break;
+        }
+        case 2: {
+            TxValidationState state;
+            CAmount tx_fee_out;
+            const CTransaction transaction{random_mutable_transaction};
+            if (ContainsSpentInput(transaction, coins_view_cache)) {
+                // Avoid:
+                // consensus/tx_verify.cpp:171: bool Consensus::CheckTxInputs(const CTransaction &, TxValidationState &, const CCoinsViewCache &, int, CAmount &): Assertion `!coin.IsSpent()' failed.
+                break;
+            }
+            try {
+                (void)Consensus::CheckTxInputs(transaction, state, coins_view_cache, fuzzed_data_provider.ConsumeIntegralInRange<int>(0, std::numeric_limits<int>::max()), tx_fee_out);
+                assert(MoneyRange(tx_fee_out));
+            } catch (const std::runtime_error&) {
+            }
+            break;
+        }
+        case 3: {
+            const CTransaction transaction{random_mutable_transaction};
+            if (ContainsSpentInput(transaction, coins_view_cache)) {
+                // Avoid:
+                // consensus/tx_verify.cpp:130: unsigned int GetP2SHSigOpCount(const CTransaction &, const CCoinsViewCache &): Assertion `!coin.IsSpent()' failed.
+                break;
+            }
+            (void)GetP2SHSigOpCount(transaction, coins_view_cache);
+            break;
+        }
+        case 4: {
+            const CTransaction transaction{random_mutable_transaction};
+            if (ContainsSpentInput(transaction, coins_view_cache)) {
+                // Avoid:
+                // consensus/tx_verify.cpp:130: unsigned int GetP2SHSigOpCount(const CTransaction &, const CCoinsViewCache &): Assertion `!coin.IsSpent()' failed.
+                break;
+            }
+            const int flags = fuzzed_data_provider.ConsumeIntegral<int>();
+            if (!transaction.vin.empty() && (flags & SCRIPT_VERIFY_WITNESS) != 0 && (flags & SCRIPT_VERIFY_P2SH) == 0) {
+                // Avoid:
+                // script/interpreter.cpp:1705: size_t CountWitnessSigOps(const CScript &, const CScript &, const CScriptWitness *, unsigned int): Assertion `(flags & SCRIPT_VERIFY_P2SH) != 0' failed.
+                break;
+            }
+            (void)GetTransactionSigOpCost(transaction, coins_view_cache, flags);
+            break;
+        }
+        case 5: {
+            CCoinsStats stats;
+            bool expected_code_path = false;
+            try {
+                (void)GetUTXOStats(&coins_view_cache, stats);
+            } catch (const std::logic_error&) {
+                expected_code_path = true;
+            }
+            assert(expected_code_path);
+            break;
+        }
+        case 6: {
+            (void)IsWitnessStandard(CTransaction{random_mutable_transaction}, coins_view_cache);
+            break;
+        }
+        }
+    }
+}
diff --git a/src/test/fuzz/util.h b/src/test/fuzz/util.h
index f72d9380eb..9d0fb02128 100644
--- a/src/test/fuzz/util.h
+++ b/src/test/fuzz/util.h
@@ -8,6 +8,7 @@
 #include <amount.h>
 #include <arith_uint256.h>
 #include <attributes.h>
+#include <coins.h>
 #include <consensus/consensus.h>
 #include <primitives/transaction.h>
 #include <script/script.h>
@@ -149,4 +150,15 @@ NODISCARD bool AdditionOverflow(const T i, const T j) noexcept
     return std::numeric_limits<T>::max() - i < j;
 }
 
+NODISCARD inline bool ContainsSpentInput(const CTransaction& tx, const CCoinsViewCache& inputs) noexcept
+{
+    for (const CTxIn& tx_in : tx.vin) {
+        const Coin& coin = inputs.AccessCoin(tx_in.prevout);
+        if (coin.IsSpent()) {
+            return true;
+        }
+    }
+    return false;
+}
+
 #endif // BITCOIN_TEST_FUZZ_UTIL_H